1. Technical Field
The present disclosure relates to the field of semiconductor structure and semiconductor process, and more particularly, to semiconductor flip-chip bonded device and semiconductor process for manufacturing the same.
2. Description of the Related Art
In a conventional semiconductor flip-chip bonding method, a barrier layer of nickel (Ni) material is coated to a copper pillar of an upper die, and a solder is formed on the Ni barrier layer. Then, the upper die is placed on a bottom die or a substrate, so that the solder on the copper pillar contacts the pad of the bottom die or the substrate. After a reflow process, the solder is melted to join to the pad so as to form a semiconductor flip-chip bonded device.
During the reflow process, the solder may react with the pad of the bottom die or the substrate so as to form intermetallic compounds (IMC). Typically, the material of the solder is a tin silver alloy (e.g., SnAg), the material of the pad is copper (Cu), and the material of an IMC is thus a combination of tin, silver and copper, such as Cu6Sn5, Ni6Sn5, Cu3Sn4 or Ni3Sn4. IMCs can make the bonding between the solder and the pad tighter. However, if the pad is thin, the whole pad may react with the solder so that the pad cracks. In addition, a thicker IMC layer will reduce the shear strength of the semiconductor flip-chip bonded device because the IMCs are brittle. Moreover, if the solder is very thin (e.g., less than 30 μm), the volume ratio of the IMCs to the solder can exceed 80%, which can result in joint crack.
Thus, a new semiconductor device and semiconductor process for controlling amounts of IMCs are desirable.